docs(docker-compose): Update examples to not use vars in keys

docker-compose/examples/grafana/docker-compose.yml

@@ -3,7 +3,7 @@ services:
         image: "grafana:${GRAFANA_VERSION}"
         container_name: "grafana-grafana-${CONTEXT}"
         networks:
-            grafana-${CONTEXT}:
+            grafana-default:
         profiles: ["full", "grafana"]
         extends:
             file: common-settings.yml
@@ -21,7 +21,7 @@ services:
         image: "nginx:${NGINX_VERSION}"
         container_name: "grafana-nginx-${CONTEXT}"
         networks:
-            grafana-${CONTEXT}:
+            grafana-default:
         profiles: ["full", "nginx"]
         extends:
             file: common-settings.yml
@@ -36,7 +36,7 @@ services:
             # NGINX_USER: ${NGINX_USER}
             # NGINX_PASSWORD: ${NGINX_PASSWORD}
 networks:
-    grafana-${CONTEXT}:
+    grafana-default:
         name: grafana-${CONTEXT}
         driver: bridge
         driver_opts: